Sensor and MeasurementIntroduction to Sensor-Based Measurement Systems I

Spring, 2018

Prof. Jungkeun Park

Outline

▪ Introduction to Sensor Based Measurement Systems

– General concepts and terminology

– Sensor classification

– General input-output configuration

– Static characteristics of measurement systems

– Dynamic characteristics

– Other sensor characteristics

– Primary sensors (1.7)

– Materials for sensors

– Microsensor technology

2

Sensors in Smart Phone

3

Face ID

Barometer

Three-axis gyro

Accelerometer

Proximity sensor

Ambient light sensor

Sensors in Drone

4

Sensors in Autonomous Car

5

General Concepts and Terminology

▪ Measurement system (측정시스템)

– Set of elements needed to measure the measurand

– Function of measurement system is the objective and empirical a

ssignment of a number to a property or quality of an object or ev

ent in order to describe it.

– Result of measurement must be independent of the observer (ob

jective) and experimentally based (empirical).

▪ Objectives of measurements

– Process monitoring

– Process control

– Experimental engineering assistance

6

Measurement Systems

7

Measurement System Application

▪ Sensor and control system

System model

(causal, linear,

time invariant,..)

Sensor/

transducerFilter Controller Actuator

Physical phenomena를다른물리적신호로검출, 변환

Acquired signal을유효한목적을위해변환, 추출, 혹은추정

System의내부상태혹은출력을 desired value로유도

제어신호로부터 system을구동하기위한환원부

input output1. GPS system

2. IMU and motion simulator

3. inverted pendulum control

Transducers, Sensors, and Actuators

▪ Transducers

– 어떤물리적형태의신호를 다른물리적형태의신호로 변환하는소자; energy converter

– ex) bimetal, speaker, microphone, motor, magnetic compass,…

– Ideally, we assume no ‘loading effect’ in transducer, yet in

practice measured system is perturbed by the measuring action

– 6 signal types

• Mechanical

• Thermal

• Magnetic

• Electric

• Chemical

• Radiation (including light)

9

Transducers, Sensors, and Actuators

▪ Sensors

– 어떤물리적형태의신호를 전기적신호로변환하는 transducer

– input transducer

– 예) 온도센서, 유압센서, 가속도센서….

▪ Actuators/Effectors

– Output transducer

– 예)모터, 로봇손, 발, 히터등

10

Advantages of Electronic Measurement

Systems

▪ 적당한재료를택하면전기적신호가아닌신호 (non-

electric quantity)도모두측정가능– e.g., thermistor

▪ 피측정체로부터에너지를거의뺏지않음– Negligible energy drained from process being measured

▪ Easy and efficient integrated circuits exists for electric

signal

▪ Easy information display or recording

▪ Signal transmission is more versatile

11

Transducers, Sensors, and Actuators

▪ Transducer generally implies– Input-output quantities are not generally the same

– It means even a sensor may not be a transducer

• e.g., galvanometer

▪ Input vs. output transducer– Physical signal to electric signal; sensor/detector

– Electric signal to display or actuation; actuator/effector

▪ Concept of primary sensor– Usually, in case of mechanical sensors

– It converts measurand into a measuring signal

– ex. Pressure sensor with diaphragm

• Pressure difference mechanical stress electrical signal

Transducers, Sensors, and Actuators

▪ Examples of pressure sensor

– Concept of primary sensor

Barometric sensor

Amplified pressure sensor

Customized pressure sensor

Pressure sensor

Signal Conditioning and Display

▪ Signal conditioner

– Elements that improve electric sensor output signal so that it

gets more suitable for signal transmission, display, or recording

– Fundamental functions

• Amplify, level shift, filtering, impedance matching, modulation,

demodulation

– In some standards,

• tansmitter = sensor + signal conditioner

– Example

• Signal conditioner for AD converter

• Sensor output: millivolt range with high frequency noise

• AD converter: input range is about 10 Volt, and the input voltage

should be DC or slowly time varying, low input impedance

– What is needed?

14

15

Interfaces, Data Domains, and Conversion

▪ Data domain

– Name of a quantity used to represent or transmit information

– i.e., domains of analog (volt, charge), digital, time (period, frequency, phase)

▪ Interface

– Signal-modifying elements that operate in the electrical domain

– eg. ADC

▪ Conversion

– Signal modification from one (sub-)domain to another (sub-)domain

16

Direct & Indirect physical measurements

▪ Direct physical measurements– Yield quantitative information about

physical object or action by direct comparison with reference quantity

• Ex) Weighing scale, thermometer….

▪ Indirect physical measurements– Quantitative information is calculated

by applying an equation that describes the law relating other quantitiesmeasured with a device, usually an electrical one.

• Ex) Electrical resistance (Ohm) measurement, mechanical power measurements (torque times angular rate), traveled distance.